1. Industrially Applicable Field
The present invention relates to a method for the processing of silver halide photographic light-sensitive materials, and more particularly to a bleach-fix monobath processing, which is required for the purpose of the rapid processing of high-speed silver halide color photographic light-sensitive materials.
2. Description of the Prior Art
Present-day silver halide photographic light-sensitive materials are desired to have higher light-sensitivity and more improved image quality. In order to obtain a higher sensitivity various endeavors have hitherto been made in the aspects of the formation of silver halide particles, silver halide composition, chemical sensitization, spectral sensitization, and the like, and these have fairly succeeded to date. However, even if all the known methods of increasing the sensitivity were used, those obtained in color light-sensitive materials would still not be sufficient. Another effective method for increasing the sensitivity of silver halide color photographic light-sensitive materials is to make larger the silver halide particle size. However, this method increases the sensitivity all right, but deteriorates image quality, particularly, the graininess and sharpness. The graininess of the finally obtained color image in color light-sensitive materials is affected not only by the graininess of the silver image but by the developing agent and coupler used, and other materials present along therewith. Effective methods for improving the image quality, particularly, the graininess and sharpness, of a color light-sensitive material include increasing the quantity of silver; using development inhibitor releasing-type couplers (generally called DIR couplers) or noncoupler-type development inhibitor compounds; and composing each of the blue-sensitive, green-sensitive, and red-sensitive layers of not less than two subcomponent layers different in the mean silver halide particle size. However, the color light-sensitive material having blue-sensitive, green-sensitive and red-sensitive layers, to which are applied such methods, has produced, in addition to the problem of the image quality such as the graininess and sharpness, new difficulties that have not ever seen before in relatively low-speed color light-sensitive materials. The difficulties are such problems that there occur increases in the mean silver halide particle size and in the coating quantity of silver for the purpose of the higher sensitization and the improvement on the image quality; an increase in the layer thickness due to the respective light-sensitive layer compositions each being of not less than two subcomponent layers; and dye loss and large deterioration of the desilvering due to the use of DIR couplers or DIR compounds.
Particularly, in the above-described color light-sensitive material, the dye loss and the desilverying characteristic during the bleaching process of the red-sensitive silver halide emulsion layer that is located nearest the support are considerable problems as compared to those of the green-sensitive and blue-sensitive layers.
That is, the above-described points, as well-known to those skilled in the art, are deathblow to the color reproduction obtained after processing the color light-sensitive material, and the slight amount of the residual silver after the processing is said to be detrimental to the preservation of the dye image, thus making it almost impossible to provide any practically usable color light-sensitive materials.
On the other hand, as the bleaching agent for use in removing the silver image from conventional silver halide color photographic light-sensitive materials, there have been used such oxidizing agents as red prussiate of potash, bichromates, persulfates, iron chloride, and the like, but these agents are undesirable in respect of having toxicity and corroding members of the processor used. Therefore these agents are considered unable to be practically satisfactorily used.
In recent years, metallic complex salts of aminopolycarboxylic acids have become used as the oxidizing agent for a bleaching bath or bleach-fix bath for the reason that they have no problem at all in the toxicity.
However, such metallic complex salts of aminopolycarboxylic acids are weak in the oxidizing power, so that they have the disadvantage that the rate of their bleaching of the image silver is low, the disadvantage making it impossible to carry out any monobath bleach-fix processing which is essential for the rapid processing of a high-speed silver halide color photographic light-sensitive material.
In fact, an ethylenediaminetetraacetic acid iron (III) salt which is considered strongest in the bleaching power among the metallic complex salts of aminopolycarboxylic acids is partly used practically also as the bleach-fix bath, but is insufficient in the bleaching power for high-speed silver halide color photographic light-sensitive materials, particularly, those color paper for camera use, color negative and color reversal films for camera use, which all contain silver iodide as their silver halide, and even when these light-sensitive materials are processed over an extensive period, a very slight amount of the image silver remains undesilverized. This phenomenon significantly appears in the case of a bleach-fix bath containing a thiosulfate as the oxidizing agent together with a sulfite because the oxidation-reduction potential is lowered.
In an attempt to solve these problems, as described in Japanese Patent Examined Publication No. 8506/1970, Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 280/1971, Japanese Patent Examined Publication No. 556/1971 and Japanese Patent O.P.I. Publication No. 5630/1974, bleach accelerators have been used to be added to those bleach-fix baths comprised principally of ethylenediaminetetraacetic acid iron (III) salt, but the use of such bleaching accelerators do not necessarily provide a satisfactory bleaching effect or has such a problem as producing less-soluble precipitates as the silver is dissolved to be accumulated, and the like, so that the accelerator cannot be practically used at all in the bleach-fix bath for high-speed silver halide color photographic light-sensitive materials.
As another method, there is carried out an ethylenediaminetetraacetic acid iron (III)complex salt-containing bleach-fix bath processing at a low pH at which the bleaching power is strongly displayed. In this process, however, there occur such vital problems that the thiosulfate and sulfite present together with the complex salt tend to be decomposed to make the bleach-fix bath unstable, and a cclor developed dye, particularly, cyan dye, tends to become a leuco compound, so that the dye does not sufficiently form its intrinsic color.
In order to solve such problems if the processing is effected at a higher pH, it causes such further disadvantages that, although the occurrence of the leuco compound of the cyan dye becomes reduced, the desilvering ability becomes lowered as the pH increases, and further there appears a dye stain (hereinafter called stain) due to the coupling reaction of the oxidized product of a developing agent with the residual coupler, so that any satisfactory bleach-fix processing cannot be achieved.
As another solution to such problems there is conceivable such a method that into a silver halide color photographic light-sensitive material is incorporated a leuco dye-less-formable coupler, particularly, a 2,5-diacylamino radical-having phenol-type cyan coupler, and this color light-sensitive material is processed in a bleach-fix bath with its pH not more than 5 containing ethylenediaminetetraacetic acid iron (III) complex salt as the oxidizing agent, or in a bleach-fix bath containing glycol-ether diaminetetraacetic acid iron (III) complex salt. However, even if the degree of the formation of the leuco compound of the cyan dye and the bleaching rate were as good as expections, the sulfite and thiosulfate present together would be significantly decomposed in a low-pH bleach-fix bath, making the bath unstable, so that the bleach-fix bath is not usable practically. Therefore, in the case where the bleach-fix processing of high-speed color light-sensitive materials is carried out by use of a conventional ethylenediaminetetraacetic acid iron (III) complex salt as the oxidizing agent-containing bleach-fix bath, there has been no such sufficiently satisfactory bleach-fix bath as improved to solve concurrently the four problems: to increase the desilvering rate and power; to reduce the formation of the leuco compound of the cyan dye; to reduce the occurrence of stain; and to stabilize the bleach-fix bath by preventing the decomposition of, particularly, the thiosulfate.
Accordingly, it has been hoped for the realization of a monobath bleach-fix processing system for use in processing high-speed color light-sensitive materials, which is capable of satisfying concurrently these four problems that are essential for the monobath bleach-fix liquid.